It is described a method for estimating a life indicating quantity of a component (46, 48, 38, 40, 44, 36, 22, 19, 28, 50) of a gas turbine engine (10), the method comprising: measuring (77) values or amplitudes (105, 107) of at least one engine parameter over time (101), the engine parameter influencing the life of the component; using digital signal processing and determining (79) an amplitude distribution in the time domain (115) and/or an energy or power distribution in the frequency domain (117) of the measured engine parameter; accessing (81) reference data associating at least one reference amplitude of the engine parameter in the time domain and a reference life indicating quantity and/or associating at least one reference amplitude of the engine parameter in the frequency domain and a reference life indicating quantity; and determining (83) the life indicating quantity of the component based on the reference data, the amplitude distribution in the time domain (115) and/or the energy or power distribution in the frequency domain (117).